Oxygation Improves Sub-surface Drip Irrigation Efficiency

Glasshouse results have been repeated in field trials with oxygation.

We are very pro the concept of subsurface drip irrigation, as there are potential increases in watering efficiency, avoidance of wind which can influence irrigation distribution, opportunities to use recycled effluent - away from contact with people, and opportunities to arrange irrigation scheduling at your most convenient time - baesd on water availabiity and site usage. It has a lot going for it! It can also significantly reduce vandalism on sprinkler systems, often a scourge for operators.

We favour the system developed in Australia [see http://www.kisss.net.au/], which offers improved and more even distribution, especially for open space and or turf areas. We even have a few posts about the system [see posts list]. And there are other supplier systems too, but not as efficient as KISSS.

While we were aware of the potential for using air injection with subsurface irrigation, and there have been some detailed research papers published, the media release [amended slightly] below has confirmed the very real potential for the air injection option in real world situations. Yes......it was on heavy soils, something that is not that common for horticulture and definitely not an ideal soil for well used turf eg ovals, sporting fields. However, extension of the thinking may even allow further reductions in water use on predominantly urban turf areas, if similar results are obtained for lighter soils.

Air injection is not overly expensive, and can be easily installed on existing irrigation systems.

[media release partially sourced from Qld Rural News]

Irrigators may not be familiar with the term "oxygation", but for cotton water use efficiency researcher, Lance Pendergast, it is a sub-surface drip irrigation system that has delivered 12–23pc yield increases.

Mr Pendergast is a Queensland Department of Primary Industries and Fisheries rural water use efficiency development extension officer based at Emerald, and is finalising his PhD research examining the potential for SDI oxygation technology.

The 5.2 hectare sub-surface drip irrigation trial site on Tony Ronnfeldt's Emerald Irrigation Area farm, Nyang, was established seven years ago by the Department of Natural Resources and Water. This project was to evaluate water use efficiency and levels of herbicide, pesticide and fertiliser chemicals in irrigation runoff of SDI compared with conventional furrow irrigation. The site has 12 individually irrigated experimental blocks with SDI lines buried 300mm under the soil surface which are scheduled to deliver the precise volume of water to maintain optimum soil moisture in the crop root zone.

With a question mark over the below-expectation yield performance of cotton crops irrigated by SDI, Mr Pendergast's PhD project was to see if promising glasshouse experimental results using oxygation translated to the field. The trials were overseen by Central Queensland University's Professor David Midmore and have examined the potential benefits of oxygation – a technique that involves entraining air into irrigation water delivered via sub-surface drip lines. "Because of the high moisture holding capacity of the heavy soil, it was determined that the cotton plants were being subjected to episodic water logging events after each irrigation," Mr Pedergast said. "Although each event was short term, the cumulated effect incurred a final yield penalty preventing SDI irrigated cotton from achieving its full potential."

Mr Pendergast began field trialling oxygation technology three years ago using Mazzi injectors that were adjusted to deliver a 12pc air by volume mix into the water lines to alleviate the root zone water-logging. When comparing the crop performance of sub-surface drip between oxygated and non-oxygated blocks, there was a significant yield increase achieved through oxygation for the 2004-05 and 2005-06 trial crops (27pc and 16pc respectively). "The oxygation trials show that we can achieve significant increases in both yield and water use efficiency using this technique," Mr Pendergast said. "When we add up the water saving advantages and improved yield of oxygated sub-surface drip, growers who are prepared to adopt and manage the technology are in a better position to justify the high SDI capital cost of around $3500 to $4500/ha."